Choh-yi ang



28, 1959 c o -y ANG I Re. 24,674

HIGH-STRENGTH HIGH-DENSITY nmcs'rsn' BASE ALLOYS angina F11 June 26,1956 s Sheets-Sheet -1 00MPOs/7/0M L/M/TJ a; IV-M ca-Mo 16140);

I l v 21 M0, /4 mum 2 4 6 B 10 12 14 16 I8 20 Z2 Z4 70 [/Viffn) INVENTORATTORNEY July 28, 1959 CHOH-Yl ANG HIGH-STRENGTH HIGH-DENSITY TUNGSTENBASE ALLOYS 6 Sheets-sheaf.

Original Fil ed June 26, 1956 mum Em? in .INVENTOR ('HQ/l- Yf 4N6 BYATTORNEY July 28, 1959 CHOH-YI ANG Re. 24,674

HIGH-STRENGTH HIGH-DENSITY TUNGSTEN BASE ALLOYS Original Filed June 26.1956 6 Sheets-Sheet .4

FIG .5.

INVENTOR CHOH-YI ANG ATTORNEY Re. 24 6M HIGH-STRENGTH HIGH-DENSITYTUNGSTEN BASE ALLOYS Original Filed June 26, 1956 July 28, 1959 CHOH-YIANG 6 Sheets-Sheet.

FIG. 6.

FIG.7.

INVENTOR CHOH Yl ANG BY flda ATTORNEY July 28, 1959 -w ANG Re. 24,674

HIGH-STRENGTH HIGH-DENSITY TUNGSTEN BASE ALLOYS Original Filed June 26,1956 s Sheets-Sheet 6 INVENTOR CHOH'YI ANG ATTORNEY United States PatentOfiice Re. 24,674- Reissued July 28, 1959 HIGH-STRENGTH HIGH-DENSITYTUNGSTEN BASE ALLOYS Clioh-Yi Aug, Indianapolis, Ind., assignor to P. R.Mallory & Co., Inc., Indianapolis, Ind., a corporation of DelawareOriginal No. 2,843,921, dated July 22, 1958, Serial No.

594,039, June 26, 1956. Application for reissue December 23, 1958,Serial No. 782,613

5 Claims. (Cl. 29-182) Matter enclosed in heavy brackets [II appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

This invention relates to high-density tungsten base alloys, and moreparticularly, to tungsten base alloys having improved physicalproperties, such as greatly increased ultimate tensile strength, whichcould not be obtained with prior alloys of the same general type.

Heretofore, tungsten base alloys, especially a group of these alloys inwhich small percentages of nickel and copper were alloyed with thetungsten base, have been used commercially on a substantial scale forapplications where their high density and other physical characteristicshave been found to be desirable, for example, for radiation shielding,weight balancing, rotors of gyroscopes and gyrocompasses, balancecrankshafts of aeromotors, boring bars, tool shanks, and the like.Although these prior tungsten-nickel-copper alloys possessed valuableproperties in addition to their high densities, such as the possibilityof machining them to final dimensions without grinding or otherexpensive operations, they had the disadvantage of relatively lowstrength. Thus, one of the strongest known tungsten-nickel-copper alloyswas reported to have a tensile strength of only 112,000 p.s.i. Thiscircumstance has limited the use of these alloys for certainapplications, particularly as rotors of gyroscopes and gyrocompasses,where the present trend of development is toward increased rotationalspeeds requiring higher tensile strength of the structural materialsused.

It is an object of the present invention to improve tungsten basealloys.

It is another object of the present invention to provide improvedhigh-density tungsten base alloys characterized by tensile strengthsgreatly exceeding those obtainable with conventional tungsten basealloys.

It is a further object of the invention to provide highdensity tungstenbase alloys containing, in addition to the usual alloying metals ofnickel and copper, also other metals in critically controlledproportions and which will yield ultimate tensile strengths from to morethan 50% greater than those of the heretofore reportedtungsten-nickel-copper materials or of their modified alloys.

It is also within the contemplation of the invention to provide a novelmethod for the commercial production of high-density tungsten basealloys of high strength.

The invention also contemplates a novel and improved group ofhigl1-density tungsten base alloys which, as to the cost of theinitialmaterials and production, are not more expensive than presenttungsten base alloys for similar applications, wihch are characterizedby ultimate tensile strengths which were hereto unobtainable in thepresent tungsten base alloys, and which may be readily manufactured andsold on a practical and commercial scale at a low cost.

Other and further objects and advantages of the present invention willbecome apparent from the following description, taken in conjunctionwith the accompanying drawings, in which:

Fig. l is a graph indicating the composition limits of a group oftungsten base alloys embodying the invention;-

Fig. 2 is a similar graph indicating the composition limits of anothergroup of tungsten base alloys of the invention;

Fig. 3 is a graph showing the effect of sintering time on the physicalproperties of the alloys embodying the invention;

Figs. 4 to 8 are photomicrographs of the microstructure of an alloy ofthe invention made with different sintering times; and

Fig. 9 is a similar photomicrograph of the inicrostructure of aconventional high-density tungsten base alloy.

Broadly stated, the present invention is based on the discovery thathigh-density alloys of heretofore unobtainable strength and othercharacteristics may be obtained by alloying tungsten with minorproportions of copper,

nickel and molybdenum, or of copper, nickel, molybdenum and iron. Thealloys within the contemplation of the invention contain as least 65% byweight of tungsten and various amounts of nickel, copper, molybdenum andiron in controlled and correlated proportions as minor constituents, thefunction of which is to form a strong alloy matrix surrounding thetungsten or tungsten and molybdenum grains, imparting to the alloy as awhole under controlled conditions ultimate tensile strengths muchgreater than those of the conventional high-density tungsten alloys toas high as that of well annealed pure tungsten. I have found that withspecific powder characteristics and under controlled sinteringconditions the mechanical properties of the sintered alloys of theinvention may be varied within wide limts; thus, ultimate tensilestrengths from 100,000 p.s.i. to greater than 160,000 psi, andductilities from a fraction of 1% to greater than 9% in one inch may bereadily obtained. For the purposes of the present description, the termhigh-density alloy is intended to mean alloys which have theoreticaldensities not less than 13.5 gm./cc. and sintered densities at least 93%of the theoretical, that is, approximately 12.6 gm./ cc.

I am aware of the fact that it was already previously attempted to formalloys containing molybdenum in addition to tungsten, nickel and copper.However, these prior alloys have been either molybdenum-base alloyscontaining tungsten, nickel and copper only as minor constituents, orhave employed molybdenum merely to replace some or most of the tungsten,thereby to obtain alloys of lower density. In contrast to this, inaccordance with the principles of the present invention, the molybdenumis not added as a density diluting agent but is adjusted in criticallycontrolled amounts with respect to the nickel and copper contents. As aresult, the alloys of the invention, when given a proper length ofadditional sintering time at temperature after adequate densificationhas been achieved, will have, upon cooling, between tungsten, ortungsten and molybdenum grains, a binding material, which is a Ni-Cu-Moor Ni-Cu-MoW complex phase, or a Ni-Cu phase containing Mo and W insolid solution, or a complex alloy phase containing minute precipitatesof the refractory elements or other alloy phases. In any case, thismatrix is strengthened by the molybdenum addition and by the controlledsintering treatments to a degree that several compositions of theinventions under certain conditions will yield ultimate tensilestrengths approaching or equal to that of well annealed pure tungsten.

In the case of the second series of the tungsten base alloys of theinvention comprising nickel, copper, molybdenum and iron, further noveland unique results are obtained. Thus, in the presence of molybdenum,the addition of iron in calculated amounts with respect to the nickeland copper contents also functions as a matrix' strengthening agent. Theaddition of iron in limited but sufficient quantities not only improvesunder given conditions the ductility of the alloys without jeopardizingtheir high tensile strengths, but also raises the degree of response ofthese alloys to sinterin'g treatments so that additional desirablemechanical properties may be 'obtained.

The alloys of the invention may he made by powder metallurgical methods.The uniformly and intimately mixed, preferably partially or totallypre-alloyed, powders of the desired constituents, having a suitableaverage particle size (as measured with a Fisher sub sieve sizer) notgreater than 8' microns, preferably between 2 and 6 microns, with anormal particle size distribution, with or without a binder, are formedunder pressure into coherent bodies and'subsequently sinteredi'n aprotective or reducing atmosphere at suitable temperatures. Thesintering temperatures must not be lower than the liquidus temperatureof the theoretical binary Ni-Cu phase and the sintering time must not beshorter than that required at the selected temperature to produce asintereddensity at least 93 of the theoretical. As a function of theaverage particle size of the prepared powder and the sinteringtemperature, for a given composition, the sintering time after theminimum densification period may be varied to obtain desired mechanicalproperties of the sintered alloy.

In making the alloys of the invention, rather than starting out frompowders of the elementary metals, it is generally preferred to mix theoxides or other readily reducible compounds of the constituents metalsin. powder form, co-reducing the mixture of metal compounds,v forexample, by heating under reducing conditions, to a mixture or partialalloy of the elementary metals, and further treating the reduced metalor partially alloyed powder by powder metallurgical procedures.

The invention will now be more fully described with particular referenceto the accompanying drawings.

COMPOSITION LIMITS The invention is directed to improvements in heavy,or high-density, alloys, which for the purposes of the presentdescription are defined as alloys having a minimum theoretical densityof 13.5 gm./cc. and a minimum sintered density equal to 93% of thetheoretical. Calculation of the theoretical densities is based on thefollow ing densities of the individual components.

GrnJ cc. Tungsten 19:32 Nickel 8.9 Copper 8192 Molybdenum 10.2 Iron 7.87

The invention contemplates alloys within the following ranges, it beingnoted that throughout the description all percentages are intended tomean percentages by weight ('w/o):

(1) W. At least 65%.

(2) Ni+Cu+Mo+Fe Not over 35%.

( 3). Ni+Cu r 4% to 25%.

(5) M04. ...'[0.-4] '0.1 (Ni+Cu)% to-l.5

(Ni+Cu)%.

(6) Fe 0 to 1.5 (Ni+Cu)% but not over 10%.

Considering first Fig. l, the application of this graph to determine theranges covered by the first series of alloys is self-evident. As to thesecond series of alloys shown in Fig. 2, all of the alloys contemplatedby the present invention are represented by the area QRHJK, with the aidof the smaller enclosure in the upper left corner. Here alittleextrapolation is required to identify a particular alloycomposition. According to condition (6), the Fe content may approach 0%,therefore, the Ni+Cu+Mo contents (W the balance) may be first plotted inthe area QRHIK, and then the Fe content is located in the upper leftenclosure by graphic extrapolation from'th'e plotted point within :QRHIK. The method of graphic extrapolation is quite simple and becomesreadily understandable from the following:

1'. Area A (QR'SN) The maximum Fe contents in the compositions en closedby this area may vary-from 6% to 10% depending on its location in thearea in terms of Ni-l-Cu and Mo contents. For example, partialcomposition a (5.7% (NH-Cu), 6% Mo; balance W) or a (5.7% (Ni-l-Cu), 4%Mo, balanceW) may represent a large number of alloys containing Fe from0% to- Graphically, this is shown by drawing a line fromeither a or aperpendicular to the abscissa ("or parallel to'line SN"), until itintersects line RS. From this point of intersection, another line isdrawn parallel to SM until 'it meets the left boundary line of the upperleft enclosure. This terminal point is 8.5% Fe; therefore, alloyscontaining 0% to 8.5% Fe plus Ni, Cu, 'Mo and W in amounts indicated bya and a: are all within contemplation of the invention.

2. Area B (NSM) All compositions may contain 0% to 10% Fe. Graphically,this may be presented by a line drawn from any partial Ni-Cu-M'ocomposition, for example b perpen-- dicular to the abscissa, to line SM.The continuation of SMterminates at 10% Fe maximum.

3. Area C (MSTL) All compositions may contain 0% to 10% Fe. The methodofgraphic extrapolation is self-evident, as shown by the example givenin Fig. 2, i. e., c alloy.

4. Area D (LTHJKL) Graphic extrapolation is the same as for area C.However, the alloys in area D may have their maximum Fe contentsvarying'from 1 0% to 0% as a function of their Mo and Ni+ Cu contents.For example, d with 11% Mo and 16.5% (Ni+Cu) may contain up to 7.5% Fe,whereas d with the same amount of Mo but 22% for Ni+Cu can containnomorethan 2% Fe.

CONSIDERATIONS RELATING TO COMPOSITION RATIOS AND LIMITS 1. Tungsten andthe density limits The lower limit of 65% for W is specified because,under present commercial practice, for applications which requirehigh-density or heavy materials, a density of 12.5 gum/cc. (93% of atheoretical density of 1315 gm/cc.)', or higher, is considered as heavy.

'2. Ni+Cu limits and Ni/Cu ratios too much liquid phase duringsintering, which makes sintering very difficult to control. Experimentalinvestigation has indicated that unless the other components (Mo, Fe andW) were present in certain specific amounts, Ni+Cu contents higher than25% resulted in weaker alloys.

Ni/Cu ratios are important because: (a) when Ni is more than 2.5 timesCu, the sintering temperature will have to be very high to effect thesolution and precipitation of W or W and Mo; (b) when Cu is more thantwice the Ni (or Ni/Cu is less than 0.5), the formation temperature ofthe liquid phase is low, and at low sintering temperatures (for example,in the range of 1100 to 1300 C.), the solution and precipitation of W orW and Mo are diflicult to achieve. Using a higher sintering temperatureunder these conditions will result in all kinds of trouble, such aswarting, blistering, or shape distortion.

3. Mo and Fe contents These two'elements do not contribute much to theformation of a liquid phase, although Mo-Ni does have an eutecticcomposition which melts at 1300 C.

There are no Mo-Ni-Fe, W-Mo-Ni-Cu, or Mo-Ni-Cu constitutional diagramsavailable in the literature, but we may think in terms of Mo-Ni andMo-Fe and Fe-Ni systems. A Mo content exceeding the maximum of 1.5 timesNi-f-Cu (or more than 2 times Ni if maximum Ni is present in Ni-i-Cu),puts the binary Mo-Ni in a high melting phase where diifusion rates ofall elements concerned are slow. This is strongly indicated byexperimental evidence.

The addition of Fe to the Ni-Cu system will strengthen the alloy phaseto a certain extent. Since in the second series of alloys, Fe is addedonly when M0 is present in order to have high strength properties, theMo-Fe system then plays a part which may be important. If the Mo contentis greater than the Fe content, the binary phases are epsilon and delta,which inherit more properties from Mo than from Fe. When the Fe is morethan the M0, the ductility of the alpha phase (high Fe) shows up untiltoo much Fe is added, then the alloy loses strength. Therefore, maximumFe is specified as the same as maximum M0 (1.5 times Ni-l-Cu), but notmore than Experiment showed that too much Fe did Weaken the alloy,although the ductility was improved. Furthermore, the density limitsimposed by practical considerations also restrict the amounts of Feaddition due to the fact that Fe is a light element having a density ofonly 7.87 gm./cc.

From the foregoing conisderations, it appears that both Mo and Fe playimportant roles in strengthening W-Ni-Cu alloys. Their function consistsof any one or all of the following:

a. They strengthen the matrix by going into solid solutions.

b. They, when in the form of very minute (submicroscopic) precipitatesin the matrix, strengthen the alloy.

c. They slow down the rate of precipitation of W from the matrix whenthe latter is already in solution, thus strengthening the alloy.

This explanation of the strengthening phenomena also clarifies why theproperties of the alloys of the invention drop to those of conventionalW-Cu-Ni alloys after excessively long sintering. Unduly long sinteringprecipitates out W or high W and high Mo phases, accompanied, of course,by grain growth, leaving the matrix essentially comprising Ni and Cu. IfFe plays a role of precipitation hardening, the long time sintering maydevelop some phenomena equivalent to high temperature over-aging, whichresults in a softer alloy.

The addition of Fe to W-Ni-Cu-Mo in limited amounts not only improvesductility without reducing the strength, but also makes the control ofthe sintering operation less difficult. This is probably due to thecontrol of particle size of the powder during powder preparation. In thepresence of the oxides of Fe and M0, the co-reduction of the mixture ofall oxides can be easily controlled to give an average particle in thepreferred range of 2 to 6 microns. Too small a particle size is not onlyhard to handle, but also makes it difiicult to arrest the sintered alloyin the correct conditions which give high strength properties. In otherwords, due to so large a total active surface area, the action ofsolution and precipitation takes place so rapidly that strengtheningphenomena occur as soon as the compact densifies, and disappear verysoon after densification. Excessively large particle size, on the otherhand, makes it difiicult to density the compact. When a very longsintering is used to achieve densification, the alloy is already in thesoft state.

ACTUAL POWDER PREPARATION In making the alloys of the invention bypowder metallurgical procedures, it is preferred to start out fromoxides of the component metals, rather than from powders of theelementary metals. Co-reduction of those oxides is used to prepare thepre-alloyed powders, the average particle size of which should notexceed 8 microns and preferably should be between 2 and 6 microns.Oxides of W, Ni, Cu, Mo and Fe are thoroughly blended together and thenreduced at 900 to 1100 C. in dry cracked ammonia 01 hydrogen atmosphere.Particle size of the resulting powder is controlled by varying reductiontime and temperature and bed thickness.

The average particle size of typical oxide materials suitable for thepurposes of the present invention will appear from the following:

Molybdic oxide Very fine, diflicult to measure. Blue tungstic oxide11-17 microns.

Magnetite 2.3 microns.

Nickel oxide Approximately 3 microns. Cuprous oxide M Approximately 3microns.

In general, pre-alloyed powders having the desired average particle sizewithin 2 to 6 microns were obtained by loading the thoroughly blendedoxide materials having the above characteristics in stainless steeltrays with a bed thickness of about W and co-reducing them at 900-1000C. for a time, at heat, of one-half to threequarters of an hour in drycracked ammonia atmosphere. In a heat zone of approximately 2" x 8" x24" with a load of not more than 2 kilos of material, the gas flow wasabout 340 cubic feet per hour. If the particle sizes of the oxides weredifferent from the ones listed in the foregoing, the desired averageparticle size of 2 to 6 microns may [b1 be obtained by appropriatelyvarying the conditions under which the co-reduction process is carriedout. This may be accomplished by several methods which employ one ormore of the following principles:

a. Thinner bed reduces particle size.

b. Lower reduction temperature reduces particle size.

c. Shorter reduction time reduces particle size.

d. More gas flow slightly reduces particle size.

PRESSING THE POWDERS Pressing of the co-reduced and at least partiallyprealloyed powders having an average particle size not exceeding 8microns and preferably within the range of 2 to 6 microns, may becarried out with or without admixture of a binder, such as glyptal.Conventional equip-- ment may be used, such as a hydraulic press capableof exerting both top and bottom pressures: simultaneously. Pressing to agreen density of 50% to 70% of the theoretical density requires onlypressures between 10 to 30 tons per square inch. Under these conditions,the green strength of the compacts very good and no pressure cracks areevident.

SINTERING Sintering is carried out in a reducing atmosphere at 7temperatures which may be between 1350 and 1500" C., preferably between1400 and 144ll C. The sintering time may vary between 4 to 60 minutes,good results being obtained by sintering for a period between 4 to 20some property data of typical sintered alloy compositions embodying theinvention. The alloys are grouped according to sintering conditions andare arranged in the order of decreasing sintered density. Except asnoted, the perminutes, keeping in mind that very long smtenng tunescentages or rat1os of the alloy constituents are derived areundesirable. The optimum; sintermg temperatures from intendedcompositlons.

TABLE I [Ni Mo 1 .Fe u] W, Wt. N1+Gu, Cu N1+Gu Ni-l-O Sint. Simt. Smt.U.T.S Percent sample Percent Wt. N,- MO Fe Density, T emn, Time, p.s.i.E1.

Percent Cu N1. C, Ni+ Cu gmJce. 0. Mm. in 1 s9. 25 7. 05 1. 04 0. 7017.23 1, 420 130, 000 4. 5 91. 50 5. 16 1. 02 0. 35 17.23 1, 420 10 126,500 6. 0 89.30 5. 53 1. 0. 56 17.15 1, 420 10 127,300 5. 0 s9. 70 5. 470. 91 0. 49 17.14 1, 420 10 155, 000 2. 5 88. 93 7. 23 0. 96 0. 52 17.13 1, 420 10 154, 000 3. 0 87. 57 7. 1. 41 0. 69 17.08 1, 420 10 120,000 2. 0 s9. 33 7. 32 1. 98 0. 17.06 1, 420 10 120, 600 5. 0 90. 41 4.0s 1. 29 0. 75 17.06 1, 420 10 133, 300 3. 5 86. 37 7. 13 1. 43 0. so16. 94 1, 420 10 133,000 3. 0 s3. 8.07 1. 67 0. 9s 16. 1, 420 10 146,000 2. 0 s4. 72 10. 15 1.02 0. 51 16. 33 1, 420 10 141, 000 2. 5 s4. 297.02 1. 19 0. 72 16. 24 1, 420 10 135,300 5. 0 72. 15 19.63 1. 30 0. 2714. 4s 1, 420 10 133, 100 8.0 85. 00 10.00 1. 50 0. 30 16. 17 1, 410 12129, 200 5.0 85.00 10.00 1. 50 0. 50 16.03 1, 410 12 134, 700 2. 0 s5.00 6. 00 1.00 0. 33 16. 02 1,410 12 129, 300 5. 0 85.00 7. 00 1. 33 1.0015.82 1,410 12 151, 500 1. 0 s5. 00 7.50 0.88 1.00 15. 1,410 12 144, 5000. 5 s3. 00 8.00 0. 60 1.00 15. 56 1,410 12 146, 400 0. 5 80.00 10.00 1.50 0. 50 15. 4s 1, 410 12 139,500 9.8 60. 00 15.00 1. 00 0. 33 15. 37 1,410 12 130, 000 3. 2 82.00 10.50 1. 33 0. 71 15. 34 1, 410 12 139, 5000. 2 s0. 00 9.00 1. 00 1. 00 15. 30 1, 410 12 151, 600 2. 0 s0. 00 9. 001.00 0. 22 15.20 1, 410 12 121, 200 7.8 80. 00 10.00 1. 50 1. 00 15. 171, 410 12 142, 000 1. o 60. 00 10.00 0. 67 1. 00 15.05 1, 410 12 142,5000. s 75. 00 12. 50 1.78 1. 00 15.02 1, 410 12 147, 000 0.8 75. 0017.00 1. 43 0. 47 14. 92 1, 410 12 149, 900 3. 5 75.00 20. 00 1. 50 0.25 14. so 1, 410 12 121, 800 4. 0 75.00 9.00 1. 00 0.89 14. 72 1, 410 12154, 000 4. 5 75.00 15.00 1. 50 0. 33 14.62 1,410 12 141, 800 3. 0 70.00 15.00 2. 00 1. 00 14. 5s 1, 410 12 153, 500 2. 5 70. 00 20.00 1. 500. 50 14. 40 1,410 12 151,000 5. 0 70.00 15.00 1.00 1. 00 14. 33 1,41012 143, 000 2. 0 72.00 19. 1. 29 0. 27 0. 15 14.25 1, 410 12 133, 400 6.1 70.00 20.90 1. 50 0. 40 0. 10 14.21 1, 410 12 147, 500 7. 5 91.00 7.20 1. 00 0. 25 17.25 1, 400 4 127, 300 4. 0 91.00 6. 00 1. 00 0. 25 0.25 17. 1, 400 4 134, 500 4. 0 90. 40 4. s0 1. 00 0. 25 0. 75 16. 99 1,400 4 131,000 3. 0 s9. 50 6. 00 1. 00 0. 25 0. 50 16.89 1, 400 4 143,600 5. 0 39.50 6. 00 1. 00 0. 50 0. 25 16. 75 1, 400 4 149, 000 2. 099.20 4. an 1.00 0.75 0 50 16.72 1,400 4 164,100 0. 6 s9. 20 7. 20 1. 000. 50 16.71 1, 400 4 144, 200 1. 0 88.00 4. s0 1. 00 0. 75 0. 75 16.651, 400 4 161, 500 0. s 90. 40 4. 1.00 0. 75 0. 25 16.99 1, 400 a142,300 1. 9 s9. 20 4. 1. 00 0. 50 0. 75 s0 1, 400 s 138, 500 2. 8 s7.40 7. 20 1. 00 0. 75 16.38 400 s 159, 000 1. 0

1 Contents of the minor elements were determined by chemical analyses.

and times, of course, depend on the particular composi- 5 APPLICATIONSW, per N 1+0u, Ni/Gn Mo/NH-Ou Fe/NH-On' cent percent 705 1. 04 0. 70 07. 13 1. 43 Q. 80 0. l1 8. Q7 1. 67 D. 98 0.07 19.63 1.30 0; 27 0.15

COMPOSITIONS The principles of the invention are applicable to" theproduction of a very large number of high density" ma terials havingheretofore nndbtainable high strength and other desirable properties.The following Table I lists The alloys of the invention are suitable forall applications where a high-density material having high strength andgood machining properties is required. Thus, in View of their extremelyhigh strength, they are especially advantageous as gyroscope rotors, asthey can be spun at rotational speeds exceeding by as much as 50% to100% the highest rotational speeds that were heretofore obtainable withconventional high density materials Without developing a permanent setbeyond the tolerable maximum. For such applications, the alloy listedunder 6-A--2 in Table I has been found to be particularly useful. Thecomposition of this alloy is:

Percent Table II is a comparison of the average properties of alloy 6-A2of the invention and those of one .of the best conventionalheavy alloyssold on the market, composed of 90% W, 6% Ni and 4% Cu:

TABLE II QOW6Nl4011 6-A-2 Density, gmJec 16.71-16.96 16.7016.95.Hardness, R0.-. 2 1-28 3034. Endurance limit, psi.-- 65,000. Electricalconductivity, per- 14.

cent I.A.O.S. Thermal conductivity, cal./ 0.225 0.235.

cmfl/cmJsecJ C. Ooefilcrent of expansion (25- 0.00 10- 5.88X10- 900 0.)[in/in, 0.] ml to. Modulus of rupture, p.s.i 230,000. Ultimatecompressive 171,400.

strength, p.s.i. Compressive yield strength, 119,800

p.s.1. Ultimate tensile strength, p.s.i. 135,000. Tensile yieldstrength, p.s.i. 4,000. Percent elongation in one inch. 2 (Min)Proportional limit, p.s.i 2 62,000. Modulus of elasticity, p.s.i44,000,000. Hlgh temperature tensile 98,600 (300 0.). strength, p.s.i.84,000 (500 0.). Temperature limit for good 450.

oxidation resistance, 0.

From the foregoing table, the superiority of the alloy of the inventionis clearly apparent.

MICROSTRUCTURE Figs. 4 to 8 are micrographs for alloy 17D, shown inTable I, sintered at 1400 C. for 4, 8, 15, 30 and 60 minutes,respectively. All of these micrographs have been taken at amagnification of 500 diameters, using K Fe(CN) as the etchant.

Fig. 9 is a micrograph taken at the same magnification and made by usingthe same etchant, of one of the best conventional heavy alloys (90% W,6% Ni, 4% Cu), sintered under conditions (16 minutes at 1400 C.), whichwere found to be the most satisfactory for an alloy of this type.

Thev most significant changes that can be observed in Figs. 4 to 8 arethe change in grain size with sintering time. However, unlike theconventional W-Ni-Cu alloys exemplified by Fig. 9, the properties ofwhich do not appreciably change as a function of grain size, the alloysof the invention exhibit a high degree of correlation between propertiesand sintering time, therefore, grain size. (See the graph shown in Fig.3.) In the microstructure of the alloys of the invention, the visiblegrains are W, Mo, and high W and high M phases. The material betweengrains is the matrix, which is believed to be Ni-Cu base containing W,Mo, and Fe at short sintering (small grain size), and Ni-Cu basecontaining mostly Fe and very small amounts of W and M0 at long timesintering (large grain size).

Although the present invention has been disclosed in connection withpreferred embodiments thereof, variations and modifications may beresorted to by those skilled in the art without departing from theprinciples of the invention. I consider all of these variations andmodifications to be within the true spirit and scope of the presentinvention, as disclosed in the foregoing description and defined by theappended claims.

I claim:

1. A sintered high-density alloy prepared by pressing and sinteringparticles of the constituents having an average size between 2 and 6microns, said alloy consisting essentially of at least 65% by Weight oftungsten, with nickel and copper in such amounts that their combinedweight constitutes 4% to 25 of the weight of the composition and theirweight ratio is between 0.5 and 2.5, and molybdenum in an amount from[0.4] 0.1 to 1.5 times the combined weight of the nickel and copper.

2. A sintered high-density alloy prepared by pressing and sinteringparticles of the constituents having an average particle size less than8 microns, said alloy consisting essentially of at least 65 by weight oftungsten, with nickel and copper in such amounts that their combinedweight constitutes 4% to 25% of the Weight of the composition and theirweight ratio is between 0.5 and 2.5, molybdenum in an amount from [0.4]0.1 to 1.5 times the combined weight of the nickel and copper, and ironin an amount up to 1.5 times the combined weight of the nickel andcopper but not exceeding 10 by weight of the composition.

3. A high-density high-strength sintered alloy compact prepared bypressing and sintering of at least partially prealloyed particles of theconstituent metals initially having an average particle size not inexcess of 8 microns, said compact being essentially composed of at least65% by Weight of tungsten, with nickel and copper in such amounts thattheir combined weight constitutes 4% to 25% of the weight of the compactand their weight ratio is between 0.5 and 2.5, and molybdenum in anamount from [0.4] 0.1 to 1.5 times the combined weight of the nickel andcopper, said compact being characterized by a sintered density at least93% of a theoretical density of not less than 13.5 gm./cc. and anultimate tensile strength substantially higher than 112,000

4. A high-density high-strength sintered alloy compact prepared bypressing and sintering of partially prealloyed particles of theconstituent metals initially having an average particle size between 2and 6 microns, said compact being essentially composed of at least 65%by weight of tungsten, with nickel and copper in such amounts that theircombined weight constitutes 4% to 25% of the weight of the compact andtheir weight ratio is between 0.5 and 2.5, molybdenum in an amount from[0.4] 0.1 to 1.5 times the combined weight of the nickel and copper, andiron in an amount up to 1.5 times the combined weight of the nickel andcopper but not exceeding 10% by weight of the alloy, said compact beingcharacterized by a sintered density at least 93% of a theoreticaldensity of not less than 13.5 gm./cc. and an ultimate tensile strengthsubstantially higher than 112,000 psi.

5. A sintered high-density high-strength tungsten base alloyparticularly suitable for high speed rotor applications prepared bypressing and sintering of partially prealloyed particles of theconstitutent metals initially having an average particle size not inexcess of 8 microns, said alloy being essentially composed of about88.5% to 90.5% tungsten, about 2.75% to about 3.25 nickel, about 2.75%to about 3.25% copper, about 2.75% to about 3.25% molybdenum, and about1.25% to about 1.75% iron constituting the balance, said alloy beingcharacterized by a sintered density at least 93% of a theoreticaldensity of not less than 13.5 gm./cc. and an ultimate tensile strengthsubstantially higher than 112,000 p.s.i.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS 1,229,960 Humphries Jan. 12, 1917 1,453,057Williams Apr. 24, 1923 1,829,635 Davey Oct. 27, 1931 2,206,537 PriceJuly 2, 1940 2,491,866 Kurtz et a1. Dec. 20, 1949 2,620,555 Lenz Dec. 9,1952 FOREIGN PATENTS 517,442 Great Britain Jan. 30, 1940 746,212 GreatBritain Mar. 14, 1956

